Bioethanol produced by fermentation of lignocellulosic biomass from forest and agricultural products not only represents an excellent substitute for fossil fuels, but it is also more advantageous than sugar or starch-derived bioethanol from an economical, energetic and environmental point of view (Farrel et al., 2006 Science 311:506-508). One of the most popular bioethanol process concepts is based on a chemical hydrolysis of the hemicellulose part (pretreatment), an enzymatic hydrolysis of the cellulose and fermentation of the resulting sugar solution using baker´s yeast Saccharomyces cerevisiae.
However wild type S. cerevisiae is unable to utilise the pentose sugars xylose and arabinose that account for a significant portion of lignocellulosic biomass (Hayn et al. 1993, in: Bioconversion of forest and agricultural plant residues. CAB International, Wallingford UK, 33-72). Also, the fermentation performances of S. cerevisiae are affected by the presence of inhibitors released during the pretreatment step, namely furan derivatives (furfural and hydroxymethylfurfural (HMF)), weak acids (mainly acetic acid, formic acid and levulinic acid) and phenolic compounds.
Lund University has for the past 15 years constructed and characterised recombinant strains of laboratory and industrial S. cerevisiae strains that are capable of fermenting the pentose sugars xylose and arabinose in the presence of lignocellulose inhibitors, using notably metabolic engineering, evolutionary engineering and classical yeast genetics. This paper reviews the major contributions of LU to the field.